A) Field of the Invention
The present invention relates to a semiconductor device manufacture method, and more particularly to a method of manufacturing a semiconductor device having side wall spacers.
B) Description of the Related Art
Dry etching is performed by using etching gas in plasma state. By monitoring emission of etching byproducts, etching can be monitored. As an etching object is completely removed, emission by etching byproducts of the etching object extinguishes. Even if the etching object is not completely removed, if the area of the etching object is reduced, the emission intensity lowers.
In most of manufacture processes for a MOS transistor, a gate electrode of polysilicon is formed on a gate oxide film on a silicon substrate, shallow and low concentration source/drain regions (lightly doped drain, LDD) or extension regions are formed by ion implantation, side wall spacers of silicon oxide are formed on the side walls of the gate electrode, thereafter deep and high concentration source/drain regions are formed by ion implantation. The side wall spacers are formed in the following manner. A silicon oxide film is formed on the whole surface of the semiconductor substrate and anisotropically etched to remove the silicon oxide film on flat surfaces and leave the silicon oxide film only on the side walls of the gate electrode. If etching continues after the silicon oxide film is etched, or in some cases, after the gate insulating film under the silicon oxide film is etched and the silicon substrate is exposed, the surface of the silicon substrate is damaged. It is desired to detect an etching end point when the silicon substrate surface is exposed, to thereby control the etching.
JP-A-HEI-5-102089 publication discloses that emission of carbon monoxide (CO) can be utilized as etching monitor if a silicon oxide film is etched by etching gas not containing oxygen but containing fluorocarbon. For example, emission having peak wavelengths of 211.2 nm, 219.0 nm, 230.0 nm and 232.5 nm can be observed during etching silicon oxide, and cannot be observed during etching Si. An etching end point can be monitored because it is possible to observe a reduction in an emission intensity caused by a reduction in a silicon oxide surface area per unit area.